Humic-acid-containing powder, method for producing humic-acid-containing water, method for improving soil, and method for promoting plant growth

Abstract

The humic-acid-containing powder has a degree of compaction of 5-20. The degree of compaction is a value calculated by the formula {(rhoP - rhoA) / rhoP} × 100, where rhoA is the aerated bulk density of the powder and rhoP is the packed bulk density of the powder. Humic-acid-containing water obtained by dissolving or dispersing the humic-acid-containing powder in water is preferably used for soil improvement and plant growth promotion.

Description

Humic acid-containing powder, method for producing humic acid-containing water, method for improving soil, and method for promoting plant growth

[0001] The present invention relates to a humic acid-containing powder, a method for producing humic acid-containing water, a method for improving soil, and a method for promoting plant growth, and more specifically to a humic acid-containing powder having predetermined properties, a method for producing humic acid-containing water using the humic acid-containing powder, a method for improving soil using the humic acid-containing water, and a method for promoting plant growth using the humic acid-containing water.

[0002] Humic acid is believed to have effects such as promoting plant growth. For this reason, its use as a fertilizer has been proposed. Humic acid is present in soil and inland water. Specifically, humic acid is contained in lignite or peat, or exists as a metabolic product of bacterial groups. While natural humic acid is derived from animals and plants, industrially known humic acids include those that are the oxidative decomposition products of young coal such as lignite, as well as alkali metal salts or alkaline earth metal salts of these oxidative decomposition products. Patent Documents 1 and 2 describe specific methods for producing humic acid extracts and specific humic acid extracts.

[0003] Patent No. 6231059 International Publication No. 2021 / 117755

[0004] Patent Documents 1 and 2 describe a humic acid extract, that is, a liquid humic acid.

[0005] On the other hand, for ease of transportation and storage, powdered humic acid can be prepared in advance and dissolved in water at the time of use to form an aqueous solution, which can then be used as a fertilizer or soil conditioner. In fact, powdered humic acid is also available on the market.

[0006] However, according to the inventor's findings, there is room for improvement in the powdered humic acid currently available on the market in terms of industrial handling. For example, there is room for improvement in the fluidity of the powder. If the fluidity of powdered humic acid is poor, there is a concern that the humic acid cannot be discharged smoothly from a silo or hopper, or that the flow path may become clogged.

[0007] The present invention has been made in view of the above circumstances, and one of the objects of the present invention is to provide a humic acid-containing powder having good flowability as a powder.

[0008] The present inventors have completed the invention provided below and solved the above problems.

[0009] 1. A humic acid-containing powder having a degree of compression of 5 to 20. 2. The humic acid-containing powder according to 1., having a loose bulk density of 0.2 to 0.5 g / cm ３ 3. The humic acid-containing powder according to 1. or 2., wherein the median diameter D ５０ 1. A humic acid-containing powder having a particle size of 10 to 200 μm. 4. A humic acid-containing powder according to any one of 1. to 3., having a melanic index of 2 to 5. 5. A humic acid-containing powder according to any one of 1. to 4., having a moisture content of 15 mass% or less. 6. A method for producing humic acid-containing water, comprising dissolving or dispersing the humic acid-containing powder according to any one of 1. to 5. in water to produce humic acid-containing water. 7. A soil improvement method, comprising spraying humic acid-containing water produced by the production method according to 6. on soil. 8. A plant growth promotion method, comprising providing humic acid-containing water produced by the production method according to 6. to plants. 9. A humic acid-containing product having a compaction degree of 5 to 20.

[0010] According to the present invention, a humic acid-containing powder having good flowability as a powder is provided.

[0011] It is a diagram showing the structure and operation principle of a disk dryer. It is a diagram showing the shape of a stainless steel container used in the performance evaluation of the examples. It is a diagram for explaining a method for evaluating the stability of a bagged humic acid-containing powder in the examples.

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, similar components are given similar reference numerals, and descriptions thereof will be omitted as appropriate. To avoid complexity, when multiple identical components appear in the same drawing, only one of the components may be given a reference numeral, and not all of the components may be given a reference numeral. All drawings are for illustrative purposes only. The shapes and dimensional ratios of each component in the drawings do not necessarily correspond to actual objects.

[0013] In this specification, unless otherwise specified, the expression "X to Y" in the description of a numerical range means at least X and at most Y. For example, "1 to 5% by mass" means "at least 1% by mass and at most 5% by mass."

[0014] <Humic Acid-Containing Powder> The degree of compression of the humic acid-containing powder of this embodiment is 5 to 20, preferably 6.5 to 18, more preferably 8 to 17, and particularly preferably 10 to 16. The degree of compression is defined as the loose bulk density of the powder, ρ Ａ and the powder's bulk density is ρ Ｐ Then, {(ρ Ｐ -ρ Ａ ) / ρ Ｐ}×100.

[0015] The humic acid-containing powder of this embodiment has a compression degree of 5 to 20, which is thought to result in good fluidity as a powder. The reason for this is not entirely clear, but can be explained as follows. A compression degree of 20 or less means that the loose bulk density is ρ Ａ and the compacted bulk density ρ Ｐ This means that the values ​​are relatively close. In other words, a humic acid-containing powder with a compression degree of 20 or less can be said to have good fluidity, with fewer gaps between the particles constituting the powder even without the application of force. On the other hand, considering industrial productivity and manufacturing costs, it is unrealistic to manufacture a humic acid-containing powder with a compression degree close to zero. Therefore, in this embodiment, the lower limit of the compression degree is set to 5.

[0016] Incidentally, a secondary effect of a compression degree of 5 to 20 is that bags filled with humic acid-containing powder can be stacked stably. Such an effect leads to stable storage of the humic acid-containing powder and prevention of cargo collapse when transporting the humic acid-containing powder by truck, train, ship, etc. By setting the compression degree of the humic acid-containing powder to 20 or less, volumetric change of the powder can be kept small even when vibration or other external forces are applied to the bagged humic acid-containing powder. Therefore, the bagged humic acid-containing powder of this embodiment can be easily stored or transported stably.

[0017] The humic acid-containing powder of this embodiment can be produced using appropriate raw materials and an appropriate production process. A preferred example of an appropriate production process is a production process using a disk dryer. Specifically, a humic acid-containing powder having a compression degree of 5 to 20 can be produced by evaporating water from a humic acid-containing liquid (such as a humic acid extract) using a disk dryer with the disk rotation speed and drying temperature appropriately set. Based on the inventors' investigations, it is difficult to produce a humic acid-containing powder having a compression degree of 5 to 20 using any powdering method other than powdering using a disk dryer. However, this does not mean that the production method for the humic acid-containing powder of this embodiment is limited. The raw materials and production process will be described in detail later.

[0018] The humic acid-containing powder of this embodiment will now be described.

[0019] (Compressibility, loose bulk density, and packed bulk density) The compressibility of the humic acid-containing powder of this embodiment may be 5 to 20 as described above. The compressibility is preferably 6.5 to 18, more preferably 8 to 17, and particularly preferably 10 to 16. The loose bulk density of the humic acid-containing powder of this embodiment is preferably 0.2 to 0.5 g / cm ３ , more preferably 0.3 to 0.4 g / cm ３ The bulk density of the humic acid-containing powder of this embodiment is preferably 0.25 to 0.6 g / cm ３ , more preferably 0.35 to 0.5 g / cm ３By appropriately adjusting not only the degree of compression but also the loose bulk density and the hardened bulk density, it may be possible to further increase the flowability of the powder and improve the handling properties of the powder other than the flowability.

[0020] (Particle size distribution) As described above, the median diameter D of the humic acid-containing powder of this embodiment ５０ is preferably 10 to 200 μm. ５０ is preferably 30 to 150 μm, more preferably 50 to 120 μm. ５０ The fact that the particle size is a relatively large value of 10 μm or more leads to suppression of alteration and deterioration of the humic acid-containing powder of this embodiment. ５０ Humic acid-containing powders with a large D ５０ Compared to humic acid-containing powder, which has a small surface area per unit volume, it is thought that deterioration and degradation due to oxygen and moisture in the atmosphere can be suppressed. ５０ When the humic acid-containing powder has a relatively large value, the humic acid-containing powder is less likely to "repel" water when it is dissolved or dispersed in water, which tends to make it easier to prepare an aqueous solution or dispersion of the humic acid-containing powder. ５０ By making the particle size 200 μm or less, the time required for completely dissolving the humic acid-containing powder in water can be shortened in some cases. The short dissolution time leads to time savings and efficiency when dissolving the humic acid-containing powder in water to prepare humic acid-containing water and then applying the humic acid-containing water to soil or plants.

[0021] The cumulative 10% diameter of the humic acid-containing powder of this embodiment is D １０ When this is done, D １０ is preferably 10 μm or more, more preferably 10 to 50 μm, and even more preferably 10 to 40 μm. １０ is 10 μm or more, in other words, by having less than 10% of the fine particles less than 10 μm in the humic acid-containing powder, scattering of the humic acid-containing powder due to static electricity is suppressed, and the handleability of the humic acid-containing powder tends to be improved (fine particles tend to be easily scattered by static electricity).

[0022] In a similar respect, (D５０ -D １０ ) / D ５０ The value of is preferably 0.1 to 1, more preferably 0.2 to 0.9, and even more preferably 0.3 to 0.8. (D ５０ -D １０ ) / D ５０ is 1 or less, the particle size distribution of the humic acid-containing powder is ５０ This means that the particle size distribution on the small particle size side is sharper than that of (D ５０ -D １０ ) / D ５０ It can be said that the fact that (D) is 1 or less means that the ratio of fine particles that are easily scattered by static electricity in the humic acid-containing powder is small. ５０ -D １０ ) / D ５０ The preferable lower limit of 0.1 is set in consideration of ease of industrial production.

[0023] From another perspective, the cumulative 90% diameter of the humic acid-containing powder of this embodiment is D ９０ When this is done, D ９０ is preferably 80 to 300 μm, more preferably 100 to 250 μm, and even more preferably 130 to 230 μm. ９０ In other words, by making the fine particles of more than 300 μm in the humic acid-containing powder less than 10%, the amount of undissolved coarse particles is reduced, and the solubility of the humic acid-containing powder in water tends to be better. ９０ -D ５０ ) / D ５０ The value of is preferably 0.7 to 1.6, more preferably 0.8 to 1.4. (D ９０ -D ５０ ) / D ５０ The fact that the value is 1.6 or less means that the particle size distribution of the humic acid-containing powder is ５０ This means that the particle size distribution on the larger particle size side is sharper than that of (D ９０ -D ５０ ) / D ５０ The fact that the ratio of coarse particles that are likely to remain undissolved in the humic acid-containing powder is 1.6 or less means that the ratio of coarse particles that are likely to remain undissolved in the humic acid-containing powder is small. ９０ -D５０ ) / D ５０ The preferable lower limit of 0.7 is set in consideration of ease of industrial production.

[0024] D １０ , D ５０ and D ９０ The value of D can be measured in a dry state by a laser diffraction / scattering method. １０ , D ５０ and D ９０ The values ​​of D are usually based on volume. １０ , D ５０ and D ９０ The values ​​of are also values ​​on a volume basis unless otherwise specified. The measurement can be carried out using, for example, an apparatus manufactured by HORIBA.

[0025] (Melanic Index (MI)) The humic acid-containing powder of this embodiment preferably has an appropriate melanic index (MI). The MI is preferably 2 to 5, more preferably 2.0 to 5.0, even more preferably 2 to 3, and particularly preferably 2.0 to 3.0. A MI within this range is considered to mean that the humic acid in the humic acid-containing powder has an appropriate amount of hydrophilic groups. The presence of an appropriate amount of hydrophilic groups is considered to further improve the water solubility or water dispersibility of the powder. The method for measuring MI is described as steps (1) to (5) in the section "Method for producing crude humic acid product" below. However, if the particle size of the humic acid-containing powder is sufficiently small, the grinding and sieving of step (1) may not be necessary.

[0026] (Moisture content) The moisture content of the humic acid-containing powder of this embodiment is preferably 15% by mass or less, more preferably 1 to 15% by mass, even more preferably 3 to 12% by mass, and particularly preferably 5 to 10% by mass. By not having a moisture content that is too high, improved storage properties such as suppression of clumping during storage and suppression of humic acid deterioration can be expected. Furthermore, by not having a moisture content that is too high, the humic acid-containing powder tends to be less likely to adhere to the container wall. In other words, by not having a moisture content that is too high, industrial handleability such as fluidity tends to be further improved. The moisture content may be low, but does not necessarily have to be close to zero, as there is a balance between the energy cost for removing moisture and the above-mentioned improvements in storage and handleability.

[0027] (Raw material for humic acid-containing powder) The humic acid-containing powder can be produced, for example, using a humic acid extract as a raw material. The humic acid extract can be produced, for example, by first oxidizing young coal such as lignite with nitric acid to obtain a humic acid crude product, and then extracting humic acid from the humic acid crude product. Below, a method for producing a humic acid crude product and a method for extracting humic acid from the humic acid crude product will be described.

[0028] - Method for producing humic acid crude product As described above, humic acid crude product can be obtained by oxidizing young coal such as lignite with nitric acid. Young coal is coal with a low carbon content, and is defined as coal with a carbon content of 83% by mass or less. Preferably, young coal with a carbon content of 78% by mass or less is used. Such young coal is in the process of being coalified and contains many aliphatic hydrocarbon structures, making it susceptible to oxidative decomposition by nitric acid. As the young coal, one or more of peat, lignite, brown coal, subbituminous coal, etc. can be used.

[0029] When oxidizing with nitric acid, it is preferable to mix 500 to 1000 kg of concentrated nitric acid (anhydrous equivalent) per 1000 kg of young coal. The mixing time can be, for example, 20 to 60 minutes. Oxidation with nitric acid is a violent chemical reaction that involves foaming. Violent foaming can make it difficult to control the chemical reaction, so an antifoaming agent may be used. Considering that humic acid is used for soil improvement, it is preferable to use hydrophobic silica, a component similar to soil, as an antifoaming agent. Commercially available hydrophobic silica products include, for example, the SIPERNAT series from Evonik.

[0030] By adjusting the amount of nitric acid added, the melanic index (hereinafter abbreviated as MI) of the obtained humic acid crude product can be adjusted to 2.0 to 3.0. MI is an index used to classify humic acids, and is the ratio of absorbance at wavelengths of 450 nm and 520 nm in the absorption spectrum of a sodium hydroxide extract (A ４５０ / A ５２０ (Reference: Kyoichi Kumada, Chemistry of Soil Organic Matter, 2nd Edition, Academic Press (1981), Japanese Journal of Soil Science and Plant Nutrition, Vol. 71, No. 1, pp. 82-85 (2000)).

[0031] More specifically, the MI can be calculated by the following procedure: (1) The sample is crushed in a mortar, and then a 250 μm sieve is used to obtain the 250 μm sieve-passing material. (2) Approximately 10 g of the 250 μm sieve-passing material is precisely weighed into a weighing bottle with a known mass. This weighing bottle is left in a dryer maintained at 105°C for approximately 12 hours, then returned to room temperature in a desiccator and precisely weighed again. The resulting mass loss is considered to be moisture, and the moisture content of the sample is calculated. (3) 0.10 g of the 250 μm sieve-passing material (equivalent to the dry mass) and 45 mL of 0.5 mol / L sodium hydroxide solution are placed in a 50 mL centrifuge tube, and the tube is shaken at 250 rpm for approximately 1 hour at room temperature (20°C). (4) After shaking, the tube is centrifuged at 3,000 x g for approximately 10 minutes. The resulting supernatant was filtered through Advantec No. 5C filter paper to obtain a filtrate. The absorbance of the filtrate at 450 nm and 520 nm was measured using distilled water as a blank. If the absorbance at 450 nm was 1.0 or greater, 0.1 mol / L aqueous sodium hydroxide was added to adjust the absorbance to 0.8 or greater but less than 1.0, and then the absorbance at 520 nm was measured. (5) The ratio (absorbance at 450 nm / absorbance at 520 nm) was calculated and used as the MI.

[0032] An MI of 2.0 or higher, as measured as described above, means that the humic acid in the crude humic acid product has sufficient hydrophilic groups and is therefore highly water-soluble. This means that the extraction rate in water (specifically, water with a pH of 7.0 or less) is improved. Furthermore, an MI of 3.0 or lower suppresses excessive oxidation reactions, leading to reduced nitric acid costs.

[0033] The MI can be increased or decreased by increasing or decreasing the amount of nitric acid when producing crude humic acid. Generally, increasing the amount of nitric acid increases the MI. From the above perspective, it is preferable to increase the MI by increasing the amount of nitric acid, but in terms of balancing costs, the MI is preferably 3.0 or less. From the perspective of achieving both improved extraction rate and cost, the MI is more preferably 2.2 to 3.0, and even more preferably 2.2 to 2.4. Incidentally, the MI of natural humic acid is generally 1.7 or less.

[0034] (Method for extracting humic acid from humic acid crude product) Water is added to the humic acid crude product obtained as described above, or to a humic acid crude product obtained by another method, and an alkali such as potassium hydroxide is also added as needed to adjust the pH to, for example, 1 to 7, preferably 5 to 7, or 1 to 3. The liquid product thus obtained is typically stirred at 40 to 90°C for 0.5 to 1 hour, and then cooled to 40°C or below. A humic acid extract can be obtained by separating unreacted residue from the cooled liquid product by centrifugation, filter press, or the like.

[0035] The term "humic acid" in the humic acid extract will be explained below. Unless otherwise specified, "humic acid" in this specification includes both humic acid itself and humic acid salts. Examples of humic acid include natural humic acid produced in natural sources such as peat and weathered coal, and artificial humic acid produced artificially by nitric acid oxidation of lignite. Humic acid salts obtained by neutralizing natural or artificial humic acid with alkaline substances such as sodium, potassium, ammonia, calcium, and magnesium are also included. In this embodiment, humic acid obtained by nitric acid oxidation of lignite is particularly preferred. Specific examples of humic acid include humic acid, nitrohumic acid, ammonium humate, calcium humate, magnesium humate, ammonium nitrohumate, calcium nitrohumate, and magnesium nitrohumate. Fulvic acid, ammonium fulvic acid, and potassium fulvic acid are also included. Humic acid preferably includes one or both of humic acid or its salts and fulvic acid or its salts. For specific examples of humic acid, reference can be made to the description in paragraph 0020 of JP-A-2023-134372.

[0036] (Solids Concentration of Humic Acid Extract) From the viewpoints of production efficiency and drying efficiency in the production of humic acid-containing powders described below, the solids concentration of the humic acid extract is preferably within an appropriate range. The "solids concentration" refers to the components remaining when water is evaporated from the humic acid extract. The solids concentration of the humic acid extract is preferably 5 to 60% by mass, more preferably 10 to 40% by mass. Using a humic acid extract with a solids concentration of 5% by mass or more tends to enable the humic acid extract to be powdered with a relatively small amount of heat. This is preferable from the viewpoints of improving production efficiency and reducing production costs. Furthermore, using a humic acid extract with a solids concentration of 60% by mass or less facilitates the humic acid extract to spread over the disk surface more easily in the production process using a disk dryer described below. This is believed to contribute to improving drying efficiency and suppressing powder clumping.

[0037] For the method of producing a humic acid extract, reference can be made to the descriptions in Patent Documents 1 and 2.

[0038] (Method for producing humic acid-containing powder) A humic acid-containing powder can be produced by drying the humic acid extract obtained as described above or a humic acid extract obtained by another method. In this embodiment, a production process using a disk dryer is preferably adopted, whereby a humic acid-containing powder having a compression degree of 5 to 20 can be produced.

[0039] A disk dryer is a device in which a material to be dried is placed on a heated, rotating disk, which is then dried to obtain non-volatile components. The non-volatile components formed on the disk as the material dries are scraped off with a scraper, and the dried material is turned into powder.

[0040] For reference, the basic structure of a disk dryer and a method for obtaining a humic acid-containing powder from a humic acid extract using a disk dryer will be described with reference to FIG. 1 . As shown in FIG. 1 , a disk dryer includes a rotatable disk 1 and a scraper 3. The disk 1 is typically made of metal. The disk 1 is heatable. Heating can be achieved, for example, by using a hollow disk 1 and introducing heated steam into the interior of the disk 1. The scraper 3 is typically in contact with the disk 1. A humic acid extract 11 is supplied to the surface of the heated disk 1, which is rotating in the direction indicated by the arrow in FIG. 1 . The supplied humic acid extract 11 spreads thinly over the disk surface due to the centrifugal force generated by the rotation of the disk 1, forming a thin film 13. Furthermore, as the disk 1 is heated, the water in the thin film 13 evaporates, and solid humic acid precipitates on the surface of the disk 1. The solid is scraped off with the scraper 3, yielding a humic acid-containing powder 15.

[0041] As the disk dryer, for example, one manufactured and sold by Nishimura Iron Works Co., Ltd. can be used.

[0042] In this embodiment, a disk dryer is used as the device for powdering the humic acid extract, and by appropriately setting various process conditions during powdering, a humic acid-containing powder with a compression degree of 5 to 20 can be produced. The specific process conditions for producing a humic acid-containing powder with a compression degree of 5 to 20 depend on the device, but for example, when using a disk-type conduction heating liquid dryer (model: CD-500) manufactured by Nishimura Iron Works Co., Ltd., the following process conditions can be adopted: - Disk heating temperature: for example, 120 to 140°C, preferably 125 to 140°C, more preferably 130 to 135°C - Disk rotation speed: for example, 1 to 10 revolutions / minute, preferably 1 to 5 revolutions / minute

[0043] <Method for producing humic acid-containing water> The humic acid-containing powder described above can be dissolved or dispersed in water to produce humic acid-containing water. This humic acid-containing water is preferably sprayed on soil for soil improvement. When producing humic acid-containing water, the ratio of humic acid-containing powder to water is not particularly limited, but when spraying on soil, it is preferable to dissolve or disperse 1 part by mass of humic acid-containing powder in 100 to 30,000 parts by mass of water.

[0044] <Method for improving soil and method for promoting plant growth> By spraying the humic acid-containing water on soil, the soil can be improved, specifically, the soil can be improved to be suitable for plant growth. Similarly, by providing the humic acid-containing water to plants, the growth of the plants can be promoted. Specifically, by spraying the humic acid-containing water on soil in which plants grow or are planted, the growth of the plants can be promoted. Examples of plants include various edible plants.

[0045] The amount of humic acid-containing water to be applied to the soil is not particularly limited, but considering the balance between the cost and the need to obtain a sufficient soil improvement effect or plant growth promotion effect, the amount of humic acid-containing water to be applied can be, for example, 10 to 50 t / ha. In terms of humic acid-containing powder, the amount to be applied can be 0.01 to 0.1 kg / ha.

[0046] <Reference Form: Humic Acid-Containing Substance> In this specification, a humic acid-containing "powder" having a degree of compression of 5 to 20 has been mainly described. However, even a non-powdered humic acid-containing substance having a degree of compression of 5 to 20 may be industrially useful. For example, a lump-shaped humic acid-containing substance obtained by compressing a humic acid-containing powder, etc., having a degree of compression of 5 to 20 may be industrially useful.

[0047] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention.

[0048] The embodiments of the present invention will be described in detail based on Examples and Comparative Examples. However, it should be noted that the present invention is not limited to the Examples.

[0049] <Preparation of Humic Acid Extract> A humic acid extract was prepared according to the following procedure. (1) 125 kg of brown coal (lignite) with a carbon content of 77% by mass was prepared, crushed to pass through a 250 μm mesh sieve. (2) Using a 500-liter stainless steel tank, 125 kg of the brown coal and 157.5 kg of nitric acid with a concentration of 48% by mass were heated in a 70°C water bath for approximately 1 hour while undergoing an oxidation reaction. A small amount of antifoaming agent (hydrophobic silica) was used to suppress excessive foaming. A humic acid-containing solution was obtained through this oxidation reaction. (3) The resulting humic acid-containing solution was dried at 105°C to obtain a crude humic acid product. The MI value of this crude humic acid product was 2.20 (measured using the method described above). (4) Approximately 900 L of 0.5 mol / L potassium hydroxide aqueous solution was added to 100 kg of the obtained humic acid crude product, and while monitoring with a pH meter, 1.0 mol / L potassium hydroxide aqueous solution was added to adjust the pH to 6.5. A small amount of water was then added to fine-tune the solid-liquid ratio to a 1:10 ratio. (The solid-liquid ratio is defined as the amount of extraction solvent relative to the humic acid crude product. A 1:10 solid-liquid ratio is defined as the amount of solvent added to 100 kg of humic acid crude product to a volume of 1,000 L.) (5) The liquid obtained in (4) above was heated at 80°C for 1 hour. In this way, humic acid was extracted with water to obtain a humic acid extract stock solution. (6) The humic acid extract stock solution was centrifuged at a centrifugal force (xg): 3,000. The resulting supernatant was used as the humic acid extract for the production of the following humic acid-containing powder.

[0050] Incidentally, the humic acid concentration (which may be regarded as the solid content concentration) of the obtained humic acid extract was 21% by mass.

[0051] <Production of humic acid-containing powder> [Examples 1 to 3] Using a disk-type conduction heating liquid dryer (model: CD-500) manufactured by Nishimura Iron Works Co., Ltd., water in a humic acid extract was evaporated under the following conditions to produce a humic acid-containing powder. - Disk heating: The disk was heated by supplying heated steam at 132°C to the inside of a hollow disk. - Disk rotation speed: 3 revolutions / minute

[0052] The production of humic acid-containing powder using the CD-500 apparatus was carried out continuously for 10 hours. The humic acid-containing powder obtained 1 hour after the start of production was designated as the humic acid-containing powder of Example 1, the humic acid-containing powder obtained 5 hours after the start of production was designated as the humic acid-containing powder of Example 2, and the humic acid-containing powder obtained 8 hours after the start of production was designated as the humic acid-containing powder of Example 3.

[0053] [Comparative Example 1] A humic acid-containing powder manufactured by a certain company (different from Denka Co., Ltd.) was obtained on the market. This powder was used as the humic acid-containing powder of Comparative Example 1.

[0054] <Measurement of loose bulk density and packed bulk density, and calculation of compressibility> The following measurements were performed using a Powder Tester PT-X manufactured by Hosokawa Micron Corporation. [Loose bulk density] According to the instructions included with the Powder Tester PT-X, the humic acid-containing powder was allowed to fall naturally into a dedicated cup (100 cc capacity). The mass of the humic acid-containing powder was measured when the humic acid-containing powder just filled the cup. The density was then calculated based on the measured mass and the volume of the cup. The measurement was performed three times, and the average of the three measurements was used as the loose bulk density. [Packed bulk density] After measuring the loose bulk density, the humic acid-containing powder was further allowed to fall naturally into the dedicated cup, and tapped 180 times / 180 seconds. The mass of the humic acid-containing powder filled in the cup after tapping was then measured. The density was then calculated based on the measured mass of the humic acid-containing powder and the volume of the cup. The measurement was carried out three times, and the average value of the three measurements was used as the compacted bulk density. Ａ , the compacted bulk density is ρ Ｐ Then, {(ρ Ｐ -ρ Ａ ) / ρ ＰThe compressibility was calculated by the formula:}×100.

[0055] <Measurement of particle size distribution> Using a laser diffraction / scattering particle size distribution analyzer LA-960 (manufactured by HORIBA), the particle size distribution was measured in a dry state. During the measurement, the refractive index was set to 1.81. The air pressure was set to 0.40 MPa. Under these conditions, the particle size distribution (volume basis) of the powders of each example and comparative example was automatically measured under atmospheric conditions. Then, from the particle size distribution obtained, D １０ , D ５０ and D ９０ Based on these values, the value of (D ５０ -D １０ ) / D ５０ and (D ９０ -D ５０ ) / D ５０ The value of was calculated.

[0056] <Measurement of Moisture Content> The moisture content was measured using a halogen moisture meter HX204 (Mettler Toledo). The drying temperature was set to 105°C, and the moisture content was automatically measured using 1 g of powder from each Example or Comparative Example. The measurement was performed three times, and the average value of the three measurements was used as the moisture content.

[0057] <Measurement of Melanic Index (MI)> The melanic index (MI) of the humic acid-containing powder of Example 1 was measured by the method described above. The MI was 2.2.

[0058] <Evaluation: Fluidity of Humic Acid-Containing Powder> The following procedure was performed. (1) 10 g of humic acid-containing powder was placed in a stainless steel container with a flat bottom (the flat surface had a width of at least 50 mm and a depth of at least 60 mm) as shown in Figure 2. The powder was then leveled so that the powder surface was flat within the 50 mm wide x 60 mm deep plane. (2) The container was tilted at a speed of 1° / sec. The angle of the container's bottom relative to the horizontal plane was measured when all the powder had flowed out. The stainless steel container was placed on a stand, and the edge of the stand and the container's neck were positioned approximately flush with each other to prevent the powder that initially flowed out from accumulating at the neck of the container and interfering with the powder that subsequently flowed out. (3) Measurements were performed three times for each powder. The fluidity was evaluated based on the average of the three angles obtained. The smaller this value, the better the powder's fluidity.

[0059] <Evaluation: Stability of bagged humic acid-containing powder> Evaluation was performed according to the following procedure. (1) 250 g of humic acid-containing powder was gently filled into a 200 mm wide x 280 mm long plastic bag with a zipper, and the zipper was closed. In this manner, a plastic bag containing humic acid-containing powder was prepared. To carry out (2) below, 27 plastic bags containing humic acid-containing powder were prepared for one type of humic acid-containing powder. (2) The plastic bags containing humic acid-containing powder were stacked three high, with nine bags per high (3 x 3), as shown in Figure 3. Stable, even stacking was evaluated as "good," while stable, flat stacking was evaluated as "poor" when the powder in the bag became tilted due to compression or other reasons, making stable stacking difficult.

[0060] Various information is summarized in the table below. In Examples 2 and 3, D ５０ However, based on common sense, it is believed that the particle size distributions of Examples 2 and 3 are not significantly different from that of Example 1.

[0061]

[0062] As shown in Table 1, the humic acid-containing powders of Examples 1 to 3, which had a degree of compression in the range of 5 to 20, had better fluidity as a powder than the humic acid-containing powder of Comparative Example 1, which had a degree of compression exceeding 20. In addition, the bagged humic acid-containing powders of Examples 1 to 3 could be stacked stably.

[0063] This application claims priority based on Japanese Patent Application No. 2023-190591, filed November 8, 2023, the disclosure of which is incorporated herein in its entirety by reference.

[0064] 1 disk 3 scraper 11 humic acid extract 13 thin film 15 humic acid-containing powder

Claims

1. Humic acid-containing powder with a compression degree of 5 to 20.

2. The humic acid-containing powder according to claim 1, having a loose bulk density of 0.2 to 0.5 g / cm ３ A powder containing humic acid.

3. The humic acid-containing powder according to claim 1 or 2, having a median diameter D ５０ A humic acid-containing powder having a particle size of 10 to 200 μm.

4. The humic acid-containing powder according to claim 1 or 2, wherein the humic acid-containing powder has a melanic index of 2 to 5.

5. A humic acid-containing powder according to claim 1 or 2, having a moisture content of 15 mass% or less.

6. A method for producing humic acid-containing water, which comprises dissolving or dispersing the humic acid-containing powder according to claim 1 or 2 in water to produce humic acid-containing water.

7. A method for improving soil, which comprises spraying the humic acid-containing water produced by the method according to claim 6 onto soil.

8. A method for promoting plant growth, which comprises providing plants with humic acid-containing water produced by the method according to claim 6.

9. Humic acid content with a compaction degree of 5-20.